LOSARTAN POTASSIUM

Clinical safety rating: avoid

NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.

How it works

Angiotensin II receptor antagonist. Blocks the binding of angiotensin II to AT1 receptors in vascular smooth muscle and adrenal gland, resulting in vasodilation and reduced aldosterone secretion.

What the body does with it

Metabolism	Hepatic via CYP2C9 and CYP3A4; active metabolite E-3174 formed via CYP2C9.
Excretion	Losartan and its active metabolite E-3174 are eliminated via renal (35% of dose) and biliary/fecal (60% of dose) routes. Approximately 4% of an oral dose is excreted unchanged in urine, while 6% is excreted as E-3174 in urine.
Half-life	Terminal elimination half-life: losartan ~2 hours; active metabolite E-3174 ~6-9 hours. Clinically, the long half-life of E-3174 allows once-daily dosing.
Protein binding	Losartan is >99% bound to plasma proteins, primarily albumin; E-3174 is >99.9% bound.
Volume of Distribution	Losartan: ~34 L (0.47 L/kg for a 70 kg adult); E-3174: ~12 L (0.17 L/kg). Vd suggests distribution primarily into extracellular fluid.
Bioavailability	Oral bioavailability: ~33% (range 25-35%) due to extensive first-pass metabolism. IV administration yields 100% bioavailability.
Onset of Action	Oral: Within 1 hour, with peak effect at 3-6 hours. IV: Onset within minutes.
Duration of Action	24 hours (supports once-daily dosing); antihypertensive effect persists for 24 hours with chronic dosing.

Classification & Brands

Dosing & administration

50 mg orally once daily; may increase to 100 mg once daily based on blood pressure response.

Dosage form	TABLET
Renal impairment	No adjustment for GFR ≥30 mL/min/1.73m²; not recommended for GFR <30 mL/min (no data).
Liver impairment	Contraindicated in Child-Pugh C cirrhosis; use lower starting dose (25 mg once daily) in Child-Pugh A or B.
Pediatric use	Weight-based: 0.7 mg/kg once daily, up to 50 mg; titrate to maximum 1.4 mg/kg (not exceeding 100 mg) once daily.
Geriatric use	Start at 25 mg once daily; may titrate based on response, with careful monitoring for hypotension and renal function.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.

FDA category	Contraindicated
Breastfeeding	Minimal excretion into breast milk; relative infant dose approximately 1.5% of maternal weight-adjusted dose; M/P ratio not established; consider risk of hypotension in neonates; generally compatible with breastfeeding but monitor infant for adverse effects.
Teratogenic Risk

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Common Effects	Dizziness Decreased blood pressure Hypoglycemia low blood glucose level Increased potassium level in blood Increased blood urea
Serious Effects

Absolute Contraindications

["Hypersensitivity to losartan or any component","Concomitant use with aliskiren in patients with diabetes","Pregnancy (second and third trimesters)"]

Clinical Precautions

Precautions

["Fetal/neonatal morbidity and death when used in pregnancy during second and third trimesters","Hypotension in volume-depleted patients","Renal function deterioration, especially in renal artery stenosis","Hyperkalemia, especially in renal impairment or with K+-sparing diuretics"]

Clinical Tips & Counseling

Drug interactions

Loading safety data…

LOSARTAN POTASSIUM

Clinical safety rating: avoid

NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.

How it works

Angiotensin II receptor antagonist. Blocks the binding of angiotensin II to AT1 receptors in vascular smooth muscle and adrenal gland, resulting in vasodilation and reduced aldosterone secretion.

What the body does with it

Metabolism	Hepatic via CYP2C9 and CYP3A4; active metabolite E-3174 formed via CYP2C9.
Excretion	Losartan and its active metabolite E-3174 are eliminated via renal (35% of dose) and biliary/fecal (60% of dose) routes. Approximately 4% of an oral dose is excreted unchanged in urine, while 6% is excreted as E-3174 in urine.
Half-life	Terminal elimination half-life: losartan ~2 hours; active metabolite E-3174 ~6-9 hours. Clinically, the long half-life of E-3174 allows once-daily dosing.
Protein binding	Losartan is >99% bound to plasma proteins, primarily albumin; E-3174 is >99.9% bound.
Volume of Distribution	Losartan: ~34 L (0.47 L/kg for a 70 kg adult); E-3174: ~12 L (0.17 L/kg). Vd suggests distribution primarily into extracellular fluid.
Bioavailability	Oral bioavailability: ~33% (range 25-35%) due to extensive first-pass metabolism. IV administration yields 100% bioavailability.
Onset of Action	Oral: Within 1 hour, with peak effect at 3-6 hours. IV: Onset within minutes.
Duration of Action	24 hours (supports once-daily dosing); antihypertensive effect persists for 24 hours with chronic dosing.

Classification & Brands

Dosing & administration

50 mg orally once daily; may increase to 100 mg once daily based on blood pressure response.

Dosage form	TABLET
Renal impairment	No adjustment for GFR ≥30 mL/min/1.73m²; not recommended for GFR <30 mL/min (no data).
Liver impairment	Contraindicated in Child-Pugh C cirrhosis; use lower starting dose (25 mg once daily) in Child-Pugh A or B.
Pediatric use	Weight-based: 0.7 mg/kg once daily, up to 50 mg; titrate to maximum 1.4 mg/kg (not exceeding 100 mg) once daily.
Geriatric use	Start at 25 mg once daily; may titrate based on response, with careful monitoring for hypotension and renal function.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.

FDA category	Contraindicated
Breastfeeding	Minimal excretion into breast milk; relative infant dose approximately 1.5% of maternal weight-adjusted dose; M/P ratio not established; consider risk of hypotension in neonates; generally compatible with breastfeeding but monitor infant for adverse effects.
Teratogenic Risk

Warnings & precautions

■ FDA Black Box Warning

None

Side Effect Profile

Common Effects	Dizziness Decreased blood pressure Hypoglycemia low blood glucose level Increased potassium level in blood Increased blood urea
Serious Effects

Absolute Contraindications

["Hypersensitivity to losartan or any component","Concomitant use with aliskiren in patients with diabetes","Pregnancy (second and third trimesters)"]